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Improving TCP Performance over Wireless Networks

Improving TCP Performance over Wireless Networks. Project Proposal. Outline. Wireless Network TCP Challenges Design Issues Existing Research Work Research Focus and Directions References. Wireless Network. Architecture

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Improving TCP Performance over Wireless Networks

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  1. Improving TCP Performance over Wireless Networks Project Proposal

  2. Outline • Wireless Network • TCP • Challenges • Design Issues • Existing Research Work • Research Focus and Directions • References

  3. Wireless Network • Architecture • Mobile Hosts are connected to Base stations through Wireless and Base Stations are connected with Wireline Internet

  4. Wireless Network • Issues • High rate of Packet Loses • Handoff • Large RTT and RTT Variation

  5. Next one is • Wireless Network • TCP • Challenges • Design Issues • Existing Research Work • Research Focus and Directions • References

  6. TCP • Today, Majority of Application Protocols use Internet’s reliable Transmission Control Protocol (TCP). • TCP aims at providing a reliable service with aiming to provide following features… • Fairness to other flows that potentially share a channel’s bandwidth • Dynamic Discovery of current availability of bandwidth • Congestion Avoidance and Control • Optimization of Error Recovery Process

  7. TCP • Issues in Wireless • TCP only assume that Packet loss is due to Congestion • But in wireless environment Packet loss can be due to following reasons… • High bit Error Rates • Handoffs • Disconnections • TCP Only resolve the packet Loss issue by decreasing the sending rate • TCP resolution strategy degrades TCP Performance and throughput

  8. TCP • In short… • Not Capable of detecting the nature of Error but only the result of the error • Error recovery mechanism is not efficient specially in Wireless environment • Very important need of TCP features for wireless devices similar to TCP features for wireline devices

  9. Next one is • Wireless Network • TCP • Challenges • Design Issues • Existing Research Work • Research Focus and Directions • References

  10. Challenges • Propose TCP must be able perform in wireless environment similar to as current TCP in Wireline network. • Also able to deal with following characteristics of Wireless environment… • High bit Error Rate • Handoff • Disconnections • Large RTT and RTT Variation • It should be simple to implement and easy to deploy

  11. Next one is • Wireless Network • TCP • Challenges • Design Issues • Existing Research Work • Research Focus and Directions • References

  12. Design Issues • Which part of network to implement the solution? It can be following… • Sender • Receiver • Wired part of the Network • Wireless part of the Network • Hybrid Approach

  13. Design Issues • Which layer to implement the solution? It can be following… • Transport Layer • Network Layer • MAC Layer

  14. Next one is • Wireless Network • TCP • Challenges • Design Issues • Existing Research Work • Research Focus and Directions • References

  15. Existing Research Work • TCP-Probing • Indirect TCP (I-TCP) • MTCP • Explicit Bad State Notification (EBSN) • WTCP • Snoop

  16. Existing Research Work • TCP-Probing • Monitor the Network status on time out event or due to three Duplicate Acknowledgements • A structured probe segment, is initiated by sender and sender also suspends all data transmission until probe acknowledgement

  17. Existing Research Work • Indirect TCP (I-TCP) • Splits the transport link at the wireline-wireless boundary • Attempt to hide the effect of wireless losses from TCP. • Loses the TCP’s end-to-end semantics • Also causes the high overhead of two connections at boundary of wireline-wireless.

  18. Existing Research Work • MTCP • Similar to I-TCP except that the last byte of data is to acknowledged to the source only it is received by the mobile host.

  19. Existing Research Work • Explicit Bad State Notification (EBSN) • If the wireless link is in erroneous state then the base station sends EBSN message to source for every retransmission of a segment to mobile host. It will require changes at source to incorporate EBSN messages.

  20. Existing Research Work • WTCP • Congestion is detected by inter-packet separation at the receiver side. • Receiver does most of the computations for congestion control. • It requires modifications in both Mobile host and as well as Fixed host.

  21. Existing Research Work • Snoop • Implemented at Data Link Layer • Base station, boundary of wireline-wireless network, monitor packets in both directions. • Base Station cache the packets and if detect the duplicate acknowledgements then it retransmit the packet from cache to mobile host. • Sack is used when traffic is send from mobile host to fixed server. • No change required in fixed host. • End-to-End mechanisms will also be preserved. • But the Link layer needs to aware that that the segment is of TCP packet. • It can also not be implemented for encrypted headers.

  22. Next one is • Wireless Network • TCP • Challenges • Design Issues • Existing Research Work • Research Focus and Directions • References

  23. Research Focus and Directions • As transport layer seems to be most appropriate place for Error Control so my research will focus for the implementation at transport layer. • There may also include lower layers for optimization based on more precise information that could be gathered from lower layers. • My design goals will focus to cover above mentioned challenges maximally.

  24. Research Focus and Directions • My intention will be to design the mechanisms which will able to identify the nature of the error due to which packet is dropped. And design of error recovery techniques based on different nature of error. • My initial focus of implementation will be wireless part of the network.

  25. Research Focus and Directions • My initial though is that the Wieleline network will provide an interface to wireless network at connection management time to communicate its network characteristics so that during further communication my mechanism will consider these characteristics to detect the nature of the error. • To analyze the performance of identified techniques I will work on Network Simulator named as REAL.

  26. Next one is • Wireless Network • TCP • Challenges • Design Issues • Existing Research Work • Research Focus and Directions • References

  27. References • “Open Issues on TCP for Mobile Computing” by Vassilis Tsaoussidis and Ibrahim Matta • “Improving Reliable Transport and Handoff Performance in Cellular Wireless Networks” by Hari Balakrishnan, Srinivasan Seshan and Randy H. Katz • “Congestion Control for High Bandwidth-Delay Product Networks” by Dina Katabi, Mark Handley, Charlie Rohrs • “Comparative Study of Various TCP Versions Over a Wireless Link with Correlated Losses • Presentation on “Introduction to TCP in Wireless Networks by Wan Gang Zeng at Simon Fraser University on July 2003 • 15th lecture of Topics in Internet Research on Wireless TCP by Satyam Sharma on February 2003

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